Watermelon variety trials have been held in Georgia for the past 8 years (1998–2005). Over this period of time, 165 varieties have been evaluated in the trials with 43 entries in the trial ≥2 years. Average yields have ranged from 13,267 lb/acre in 2005 to 45,867 lb/acre in 2002. Lower average yields reflect problems such as poor weed control. There was a concomitant increase in coefficient of variations (CVs) with lower average yields. Over the 8 years, the CV has ranged from 26% to 78%. Soluble solids have ranged from 8.7 in 1999 to 10.8 in 2004. Soluble solids CVs, however, remained relatively constant and ranged from 8% to 14%. The percent triploids ranged from 9% to 64% of entries over the 8 years. Trends over the 8 years included increasing percentage of triploids and the introduction of mini melons.
George E. Boyhan
George E. Boyhan
Plot size and number of replications were evaluated for watermelon [Citrullus lanatus (Thunb.)] over a 3-year period. Four different methods were used, including plotting basic unit plots against changes in cvs, Hatheway’s method for detecting a true difference as a percent of the mean with a 20% threshold, Bartlett’s homogeneity of variance test, and computed least significant differences (lsds). An initial evaluation was done in a trial with several varieties. Plotting cv against number of basic units using plots with different watermelon varieties suggests a plot size of ≈7 basic units (1 basic unit = 3.34 m2). With a single variety and basic units of 6.69 m2 for inside rows, the plot size was ≈4 basic units and for the outside row 5 basic units. With plot sizes of 2.23 m2, the number of basic units per plot was estimated at ≈5 basic units. Bartlett’s test suggests larger basic unit plot sizes of 14 to 20 with a 3.34-m2 basic unit size with multiple varieties. With a single variety, 4 to 8 basic unit plot sizes are required with 6.69-m2 basic unit size. Results were unreliable with 2.23-m2 plot sizes using Bartlett’s test. Computed lsds, which were 5% of the mean or less, could be achieved with plots sizes of 10 basic units and five replications with 3.34-m2 basic unit plots and using multiple varieties. Other combinations meeting these criteria included 14 basic unit plots and two or three replications. With a 6.69-m2 basic unit size, plots of 6 basic units and four replications would meet the 5% criteria. Finally, with the 2.23-m2 basic unit size, a plot size of 8 basic units and three replications would result in an lsd of 5% of the mean. Results with Hatheway’s method were similar to plots of basic units against cv. Hatheway’s method also has an estimate of number of replications and with 3.34-m2 basic unit, the 20% threshold of detecting true differences occurred with 10 to 14 basic units and four replications. For fruit size, firmness, and soluble solids, the basic unit plot sizes ranged from 5 to 7. Plot size estimates were larger with 6.69 m2 compared with 2.23 m2 for fruit characteristics.
George E. Boyhan and Joseph D. Norton
Muskmelon (Cucumis melo L.) breeding line AC-82-37-2 was identified as having resistance to alternaria leaf blight caused by Alternaria cucumerina (Ell. and Ev.) Elliot. An analysis of this resistance with a three-factor scaling test indicated that both additive and dominance effects were highly significant. The x2 value indicated that there were epistatic effects as well. The six-factor scaling test revealed no significant dominance effect, but the additive and homozygote × heterozygote epistatic interaction effects were highly significant.
George E. Boyhan and C. Randy Hill
This study evaluated poultry litter, commercial organic fertilizer, and compost for organic production of onion (Allium cepa) transplants within the Vidalia onion growing region of southeastern Georgia. Two field experiments were conducted. The first experiment tested six rates of poultry litter (0–10 tons/acre). The second experiment tested a factorial combination of two rates of nitrogen (N) (0 and 130 lb/acre) and three rates of compost (0, 5, and 10 tons/acre). Seedling weight, length, and diameter were measured ≈10 weeks after sowing. Poultry litter had a significant increasing linear effect on plant weight and diameter. There was also a significant increasing quadratic effect on plant length. Commercial organic fertilizer (3N–0.9P–2.5K) at 130 lb/acre N had a significant effect on plant length, but compost at 0, 5, or 10 tons/acre did not affect plant length. There were organic fertilizer by compost interactions for plant weight and diameter. There was a significant effect on plant diameter with organic fertilizer (130 lb/acre N) and 10 tons/acre compost, but there was no fertilizer effect on plant diameter at 0 or 5 tons/acre compost. The interaction effect on plant weight indicated there was a significant effect from fertilizer with 5 and 10 tons/acre compost, but not with 0 tons/acre. Based on this study, nutrition should not be a problem in producing organic onion transplants in southeastern Georgia. Four to 6 tons/acre fresh poultry litter should be adequate for producing good quality transplants. An alternative approach of using organic fertilizer at a rate of 130 lb/acre N with 5 to 10 tons/acre compost can also be used to produce good quality transplants.
George E. Boyhan and Reid L. Torrance
Suzanne Stone, George Boyhan, and Cecilia McGregor
Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] cultivars exhibit diverse phenotypic traits, yet are derived from a narrow genetic base. Heirloom cultivars, and to a lesser extent modern open-pollinated (OP) cultivars, are perceived to contain vital genetic variation that is critical for biodiversity conservation and crop improvement. The objective of this study was to characterize the diversity of six heirloom and open-pollinated watermelon cultivars that are popular among U.S. organic, direct-market, and home gardeners. An additional evaluation was conducted to determine whether significant phenotypic and genotypic variation existed among seed lots sourced from different commercial seed vendors. Important horticultural traits such as days to germination, days to first flower, yield, and fruit quality were measured over two field seasons. Genetic diversity was estimated using 32 simple sequence repeat (SSR) markers. Significant differences in horticultural traits among seed lots in both years were observed only in days to germination and first male flower, which may be a consequence of vendor differences in seed storage and quality control. Heirloom ‘Moon and Stars’ and modern OP ‘Sugar Baby’ were the most genetically distinct from the other cultivars and heirloom ‘Georgia Rattlesnake’ was determined to be highly related to the modern OP ‘Charleston Gray’. The two heirloom cultivars were observed to have lower average gene diversity than the modern cultivars. Heirloom ‘Moon and Stars’ contained significant genetic variation among seed lots, yet heirloom ‘Georgia Rattlesnake’ contained none. These findings suggest that genetic variation can be more accurately attributed to pedigree and foundation seed maintenance practices than to the “heirloom” designation per se. The variation reported in this study can be used to inform conservation and breeding efforts.
Manish K. Bansal, George E. Boyhan, and Daniel D. MacLean
Vidalia onions (Allium cepa) are a branded product of southeastern Georgia marketed under a federal marketing order. They are short-day, yellow onions with a Granex shape that are susceptible to a number of diseases postharvest, limiting the amount of time they can be marketed. Postharvest treatments and storage methods can help extend their marketability. Thus, the objective of this study was to evaluate these postharvest treatments and storage conditions on quality of three Vidalia onion varieties: ‘WI-129’, ‘Sapelo Sweet’, and ‘Caramelo’. All varieties were undercut, then either harvested immediately (zero cure), field cured (2 days), or forced-air heat cured (3 days at ≈37 °C) when judged mature. ‘WI-129’, ‘Sapelo Sweet’, and ‘Caramelo’ represent early, midseason, and late varieties, respectively. Bulbs were then sorted and stored in refrigerated storage [0–1 °C, 70% relative humidity (RH)], sulfur dioxide (SO2) (1000 mg·L−1 in 2010 and 5000 mg·L−1 in 2011, one time fumigation) followed by refrigeration, ozone (O3 (0.1–10 mg·L−1; continuous exposure, 0–1 °C, 70% RH), or controlled-atmosphere storage [3% oxygen (O2), 5% carbon dioxide (CO2), 0–1 °C, 70% RH]. After 2 and 4 months, bulbs were removed from storage, and evaluated after 1 and 14 days for quality and incidence of disorders. ‘Caramelo’ had the lowest percent marketable onions after curing in 2010, while ‘WI-128’ had the lowest percent marketable onions in 2011. There was a rain event immediately before harvesting ‘Caramelo’ that may have contributed to low marketability in 2010. Heat curing improved marketability for ‘Sapelo Sweet’ and ‘WI-129’ in 2010 compared with no curing. In 2011, heat curing resulted in more marketable onions for ‘Sapelo Sweet’ compared with no curing. Curing had no effect on ‘Caramelo’ in 2011 and field curing had the greatest percent marketable onions for ‘WI-129’ in 2011. In 2010, controlled-atmosphere storage had more marketable onions compared with SO2 for ‘Caramelo’ and was better than simple refrigeration or O3 with ‘WI-129’. In 2011 refrigeration, controlled-atmosphere storage, and O3 were all better than SO2 with ‘Caramelo’. ‘Sapelo Sweet’ and ‘WI-129’, on the other hand in 2011, had better storage with SO2 compared with other storage methods. Onions stored for 2 months had 32% and 17% more marketable onions after removal compared with 4 months of storage regardless of storage conditions for 2010 and 2011, respectively. Poststorage shelf life was reduced by about one-third, 14 days after removal from storage regardless of the storage conditions.
George E. Boyhan, Raymond Hicks, and C. Randell Hill
There has been interest in producing Vidalia onions organically among both conventional and organic growers. In the 2000–01 season we began to look at producing onions organically. Starting with conventionally produced transplants that were transplanted at standard commercial spacings on beds prepared with 10.2–15.2 cm of incorporated compost and 2,802 kg·ha–1 rate of fresh poultry litter. This was sidedressed with an additional 2,500 less/acre (2,802 kg·ha–1) poultry litter. Yields were about half of conventional onion production. In 2002–03, production of organic transplants with 10.2 cm of incorporated compost with 2.24 t·ha–1 rate of poultry litter, which was followed by an additional sidedressing of 2.24 t·ha–1 rate of poultry litter resulted in similar findings. The weight of harvested transplants was about half that of conventionally produced transplants. In the 2002–03 and 2003–04 seasons various natural mulches were evaluated for weed control. They included wheat straw, oat straw, Bermuda hay, pine straw, and compost. None of these performed better than hand weeding and the wheat straw, oat straw, and Bermuda hay actually reduced yields apparently due to allelopathic effects. Finally in the 2003–04 season rates of poultry litter from 0–22.4 t·ha–1 were evaluated for transplant production with rates of 13.4, 17.9, and 22.4 t·ha–1
yielding plants comparable to conventional transplants. Work continues in the area of organic Vidalia onion production. One of the greatest challenge for future work will be finding a cost-effective and practical method of controlling weeds in transplant production.
George E. Boyhan, Suzzanne Tate, Ryan McNeill, and Jeffrey McConnaughey
Tomato (Solanum lycopersicum) is a popular crop among organic growers, particularly open-pollinated varieties; however, there is a lack of information evaluating these varieties in comparison with commercial F1 hybrids. This study was undertaken to compare conventionally produced commercial F1 tomato varieties available in the southeastern United States with open-pollinated varieties popular among organic growers. Nineteen tomato varieties were evaluated in 2011 and 2012 using the U.S. Department of Agriculture National Organic Program guidelines; however, the land used had not been in 3 years of organic production. Staked tomatoes were grown on plastic mulch. Data collected included early and total graded yield. In general, F1 hybrid, determinate or semideterminate varieties, had the best early and total yields compared with open-pollinated varieties. HSX 8115H and ‘Celebrity’ had the highest early total yield. ‘Costoluto Fiorentino’, an open-pollinated variety, also had good early total yield, but significantly less than HSX 8115H or ‘Celebrity’. ‘Costoluto Fiorentino’ was the only open-pollinated variety among the five highest yielding varieties for early total yield. In addition, ‘Celebrity’ had the greatest total yield of all the entries tested. All of the top five varieties for total yield were F1 hybrids and either determinate or semideterminate types. ‘Costoluto Fiorentino’ had total yield of 22,046 lb/acre, which was 14.3% lower than the lowest yielding variety in the top five yielding varieties. ‘Florida Pink’ had the largest average fruit weight, which also had the lowest total yield of all the entries. Although the open-pollinated varieties, popular among organic and local growers, yielded less than F1 hybrids, they may possess characteristics of color, flavor, or texture that are desired and were not evaluated in this study. This may be an opportunity for plant breeders to develop varieties desired by local organic growers that have unique characteristics, in addition to high yields and disease resistance.
George Boyhan, Reid Torrance, David Curry, Pam Lewis, and Mindy Linton
In 1998–99, experiments were conducted to evaluate current fertility practices with plant-bed onions. In experiments in 1998 and 1999, a factorial experiment of preplant 5–10–15 and CaNO3 sidedressing indicated that CaNO3 had a significant effect on foliar nitrogen levels. CaNO3 also had an effect on stand count in 1998, but not in 1999. CaNO3 and 5–10–15 had an effect on plant height in both 1998 and 1999, with an interaction between 5–10–15 and CaNO3 in 1999. In 1999, transplants were also evaluated on an acceptability scale with 5–10–15 and CaNO3 rates resulting in significant differences in transplant acceptability. Postseedling applications of high phosphorus fertilizer were also evaluated. There were no consistent improvements in transplant growth with applications of high phosphorus fertilizers, such as 18–46–0 or 10–34–0, either on soils with very high residual phosphorus (242 lb/acre) or medium residual phosphorus (50 lb/acre). In addition, variety was not a factor in these responses.